A small animal shield, commonly known as a birdshield, is usually provided with outdoor luminaires to close off the back. Birds and other small animals including snakes will attempt to enter luminaire housings, perhaps attracted by the warmth or simply seeking shelter or a nesting place. The mode of entry is usually via the opening in the back of the housing where the mounting pipe bracket enters the luminaire. Once inside, the animal will usually touch a live electrical part and be killed but in the process, the unit is often shorted out and a service call is required to replace electrical components or perhaps the entire luminaire. Such a service call usually entails the use of a bucket truck and often requires the detouring of traffic around the work crew and equipment.
The service call necessitated by the lack of a birdshield or the failure of a birdshield to perform its intended function may cost anywhere from a fraction of the cost to an amount in excess of the cost of a replacement luminaire. Birdshields may need to be replaced occasionally because they can be damaged by small animals pecking at them or clawing them to pieces. It is therefore highly desirable to have them easily replaced in the field.
One prior approach to the need for a birdshield has been to make the birdshield an integral part of the luminaire housing which is generally an aluminum casting. Unfortunately, this does not permit a tight fit around the pipe as clearance is required to allow the luminaire housing .+-.5 degrees of leveling adjustment with respect to the pipe. The integrally cast birdshield also has to be sized for the largest pipe size (23/8" O.D.) intended to be accommodated in the slipfitter. This means that an excessive gap remains when smaller pipe sizes are used.
Another approach has been to provide a separate birdshield as a loose piece of material, for instance of plastic, fiberboard or metal, having an aperture sized to fit arond the pipe bracket. The birdshield may be simply taped to the inside of the luminaire and the installer is expected to remove it and fit it around the pipe bracket at the time of installation of the luminaire. In practice many installers forget or will not bother to install the birdshield so that the luminaire is left without any barrier to small animals entering through the back of the unit.
A more successful approach to the birdshield problem has been one wherein a separate birdshield is held captive in he luminaire by passing the luminaire mounting bolts through holes in the unit. This eliminates the need to rely on the installer to fit the birdshield around the pipe bracket. But it increases the luminaire assembly labor since the assembler is now required to hold the birdshield in place with its two holes aligned with those in the luminaire housing and must then drive in the slipfitter bolts. Another problem created by this design is that when the birdshield requires replacement, the mounting bolts holding the luminaire to the pipe bracket have to be completely removed in order to install the new birdshield.